Proof of 1+1=2: Maths Explanation & Examples

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Discussion Overview

The discussion revolves around the proof of basic arithmetic operations, specifically the assertion that 1+1=2. Participants explore the foundations of arithmetic, the role of axioms, and the definitions of numbers and operations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant requests a proof for the statement 1+1=2 and seeks guidance on where to start.
  • Another participant references "Principia Mathematica" as a source that contains a lengthy proof in symbolic logic, suggesting a degree-level understanding is necessary.
  • A different participant questions the existence of simpler proofs and asks for the proof of 1*1=1, indicating a desire for foundational understanding.
  • One participant argues that at some point, axioms must be accepted without proof, listing several axioms of arithmetic that are considered self-evidently true.
  • Another participant emphasizes the need to define addition before proving 1+1=2, suggesting that the definition of real numbers and sets plays a crucial role in this discussion.
  • A later reply acknowledges the previous arguments and connects the concept of neutral elements in multiplication and addition to the proof of 1*1=1, indicating a level of clarity achieved through the discussion.

Areas of Agreement / Disagreement

Participants generally agree that some foundational concepts in arithmetic are accepted as axioms without proof. However, there remains uncertainty and differing views on the nature of proofs and definitions in mathematics.

Contextual Notes

The discussion touches on the complexity of defining real numbers and the foundational aspects of arithmetic, which may not be fully resolved within the thread.

nebbione
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Proof of 1+1=2 ?

Hi everyone! Which is the proof of the rightness of arithmetical operations ?
For example which is the proof that 1+1=2 ??
Can you link me the proof or explain how it is done or where i have to start ?
 
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Ahhh ok ok ! But there isn't a simpler proof ? and who can proof that 1*1 = 1 ?? why it is like that ? which is the proof ?
 


There aren't any proofs if you keep on asking "why?", at some point or another you're going to have to accept things as true, without proof: these are axioms. Some common axioms for arithmetic are:

1) a + (b + c) = (a + b) + c
2) a + b = b + a
3) a + 0 = a
4) a + (-a) = 0
5) a*b = b*a
6) a*(b*c) = (a*b)*c
7) 1*a = a
8) a*(1/a) = 1
9) a*(b+c) = a*b + a*c

There are more formal definitions using set theory. Anyway, the idea is to make the axioms as simple as self-evidently true as possible, and then derive everything else from them.

Also, have you heard of the parallel postulate and non-Euclidean geometry? That's quite interesting.

EDIT: Although, re-reading your post, you may have meant something different with your first question. You could think of 2 as being defined as the answer to 1 + 1.
 


As the previous poster said, at some point, there are no proofs. Before we can prove 1+1=2, we have to define what addition of two real numbers. And we define that ... how? We just take it as something that "is." Real numbers prove difficult to define, but it turns out that once we have sets defined (sets may be what we have to take for granted,) it's possible to define real numbers. This is part of why some people think we invented mathematics, but that's a thread in the Philosophy forum.
 


OK nice argument! I understand now! Doing some study in linear algebra i remember about neutral element in multiplication (that is 1) and neutral element in addition (that is 0)
so i can proof that 1*1 is equal to 1 by this axioms right ?
Now it's clear
 

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